The invention relates to a flexible shaft for an endoscope, comprising a shaft body which, in the longitudinal direction of the shaft, has a first portion with a first degree of flexibility, and, proximally from the first portion, has at least a second portion with a second degree of flexibility which is less than the first degree of flexibility, the shaft body having, in the first portion, at least a first spring element, and, in the second portion, at least a second spring element.
The invention also relates to an endoscope comprising a flexible shaft of the aforementioned type.
An endoscope comprising a flexible shaft is also referred to as a flexible endoscope. Flexible endoscopes are used mainly for medical applications, but the present invention can also be applied to flexible endoscopes that can be used for technical purposes, for example for inspection of machinery.
Flexible endoscopes differ from rigid endoscopes in that the shaft of a flexible endoscope is of such flexibility that it can adopt a bent, strongly curved or even coiled configuration.
Flexible endoscopes of this kind are therefore suitable in particular as endoscopes for medical operations or examinations in internal body regions with branched or looped structures, for example in the gastrointestinal tract or in the airways, including the lungs.
A flexible endoscope used to examine the large intestine, in some cases with the possibility of performing a biopsy and conducting minor surgical interventions, is also called a colonoscope.
A flexible endoscope also has the characteristic that the distal end portion of the flexible shaft has still further increased mobility and flexibility so that this distal end portion, which is also called “deflecting” can be deflected, i.e. bent away from the longitudinal direction of the rest of the shaft, by means of a control device. Generally, the distal end portion can be deflected in a plane to both sides of the rectilinear setting, for example in an angle range of more than ±90°. The control device provided for deflecting the distal end portion is arranged at the proximal end of the flexible shaft and normally comprises a manually operated actuating element which is operatively connected to the distal end portion via a traction cable mechanism, so that the operating physician can suitably alter and adjust the deflection of the distal end portion to the particular requirements. The deflection of the distal end portion permits a large number of viewing directions through the endoscope.
While a high degree of flexibility of the shaft of a flexible endoscope is desired in the deflecting distal end portion, a lesser degree of flexibility, i.e. a greater stiffness of the flexible shaft, is desired in the proximal area of the endoscope shaft. The reason for this is that the flexible shaft as a whole can have a considerable length. When pushing the endoscope forwards, for example in the intestine of a patient, the pushing force must not cause the shaft to arch in the proximal area. If the shaft archs during insertion into the intestine, or even archs along with the intestine, this causes painful looping of the intestine. In other words, during insertion, the shaft of the endoscope must remain as straight as possible in the proximal area, which, in the proximal area, and despite guaranteed flexibility, requires a certain stability or a tendency of the shaft to automatically straighten out again in the event of arching.
The flexible shaft for an endoscope known from the document U.S. Pat. No. 6,485,411 comprises a shaft body constructed from a plurality of integrally connected spring elements in the manner of helical springs. The individual turns of the spring elements consist of a band-like flat material, the turns having a defined width in the longitudinal direction of the shaft.
The shaft body of this known flexible shaft has at least three portions with different degrees of flexibility. A distal portion has the highest degree of flexibility, i.e. is the most flexible; the next portion adjoining it has a lesser degree of flexibility by comparison; and the portion adjoining the latter proximally has a still lesser degree of flexibility. This known shaft accordingly has a flexibility that decreases in stages from distal to proximal.
In this known shaft, the different degrees or stages of flexibility are obtained by the fact that the width of the individual turns of the spring elements increases from distal to proximal, as a result of which the degree of flexibility decreases from distal to proximal. The document describes, however, how the different degrees of flexibility can also be obtained with equal widths of the turns in the longitudinal direction of the shaft, by different spacings between adjacent turns of the individual spring elements, which spacings, on production of the spring elements, are formed by the axial width of the material removed between the turns.
In a shaft body designed in this way, it has been found that, over the course of time, after a large number of applications, it shows signs of fatigue, and these result in an increased and undesired play of the control device for deflecting the distal end portion of the shaft. In this way, exact positioning of the endoscope in the examination or treatment area in the human body is made difficult.
It has also been found that a flexible shaft of this kind, especially in the proximal area, loses its stability as a result of the alternating loads arising during insertion and removal of the endoscope, i.e. the flexibility increases in the proximal area. This in turn leads undesirably to a situation where the pushing force applied during insertion causes the shaft to arch or buckle in the proximal area, because the tendency of the shaft to automatically straighten itself diminishes over the course of time through fatigue of the spring elements. This fatigue of the shaft body in the proximal area also has an effect on the outer jacket which surrounds the shaft body and which usually consists of a plastic tube, to the extent that the latter is inclined to crease and tear.
In contrast to that, the flexible shaft known from the document U.S. Pat. No. 4,329,980 comprises a flexible cylindrical hollow tube and a single helical spring, an end of which can be engaged with an end of the cylindrical hollow tube, whereby the flexibility of the flexible shaft can be adjusted. To this end, a mechanism for compressing the helical spring is provided at the other end of the cylindrical hollow tube, which mechanism comprises a slider which engages with the other end of the single helical spring, as well as an actuating portion for a to-and-fro-movement of the element for compressing the spring between a position in which the element for compressing the spring compresses the single helical spring, and a position, in which the element for compressing the spring is axially spaced apart from the end of the helical spring. Thus, the axial compression of the windings of the helical spring is adjustable with this flexible shaft.
The complexity and thus, cost expensive design of the slider drive for compression the helical spring is a disadvantage of this known flexible shaft.
Further, from document DE 697 23 193 C2, a treatment forceps for use with an endoscope is known, which comprises a flexible shaft made up from a closely wound stainless steel coil. The shaft comprises a portion which is easier to be bent than the remaining portion. This different degree of flexibility of the shaft is achieved by a pretension of the one portion of the stainless steel coil, wherein the pretension is such that adjacent windings of the coil are in contact with one another in order to increase the rigidity.